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Wednesday, February 10, 2010

Putting the Pieces Together: Refitting ancient stone tools

A SHORT HISTORY OF REFITTING

“Refitting” (sometimes also known as “conjoining”) can be traced back to F. C. J. Spurrel’s work at the Palaeolithic site of Crayford, England, in 1880. However, the technique’s potential has now become more widely known, thanks mostly to the relatively recent work at several later Stone Age sites, such as Pincevent and Meer in Europe, Kapthuring and East Turkana in Africa, and the Negev Desert in Israel.

WHAT IS REFITTING?

The creation of chipped stone tools involves a reduction sequence, which is characterized by the cumulative removal of raw material. When flaking stone, each stage involves the reduction of the original mass and the creation of tool fragments or manufacturing debris. This process of stone reduction is always irreversible, as each removal is permanent. Although it may be possible to make some adjustments along the way, unlike other materials such as metal or clay, it is not possible to start again with the original mass. The knapper, therefore, needs to plan his approach carefully, so that the best results are obtained during the reduction process. The basic stages of the reduction sequence include: procurement of the raw material and preliminary roughing out, trimming and shaping, and then final modification of the tool. Another (European) term for this sequence is called chaîne opératoire, although the name also includes the stage that occurs after completion of the finished tool (i.e., the maintenance/modification of the tool through use and final discard of the artifact). Lithic materials preserve well on archaeological sites due to their inorganic nature, enabling evidence from every stage of the reduction process.

Refitting includes at least partial reconstruction of the pieces of stone so that they almost resemble their original form. Flakes that have been struck from a core can be reassembled, by rejoining or fitting pieces together, much like a 3-D jigsaw puzzle. Although the process can be very tedious and time-consuming, it has the potential to tell us many things about past activities.

WHAT CAN IT TELL US?

Traditionally, refitting has been used to help reconstruct artifacts for illustrative or display purposes, or in order to obtain a better appreciation of the artifact’s original appearance. Refitting studies are now, however, being used to glean a greater understanding of archaeological record. By employing refitting studies, archaeologists are able to make inferences about:

* The depositional integrity of the area

It is possible to establish that the artifact concentrations were not merely the result of natural disturbances, but surviving evidence relating to human activity. For example, tight spatial clustering of refitted material would imply that there was little disturbance of the area.

* Organization within the site

Flake-reduction sequences and the nature of manufacturing technology within different parts of a site unit can be distinguished. For instance, large flakes with completely cortical dorsal surfaces would indicate that the very beginning of the reduction process was carried out in that area. Insights about early cognitive abilities may also be obtained from the use of manufacturing technology, such as hard-hammer (stone) or soft-hammer percussion (entailing the use of antler, bone or wood).

* Spatial distribution of lithics across the landscape

Archaeologists can compare the different characteristics in assemblage composition between two different unit areas in order to find out whether there are any associations. This may provide clues relating to behavioral patterns, such as forethought and mobility in transport distances, which is particularly important for the Palaeolithic period. For instance, two separate areas may have been used for particular stages of tool production.

WHAT DOES THE REFITTING PROCESS ENTAIL?

Although refitting has been used on a variety of materials (pottery, bone, shell, glass, metal and wood) and can involve various methodologies, for the purpose of this post I will discuss the approach I have used for stone tools.

First and foremost, it is important to ensure that all pieces to be refit are labeled accordingly, so that they can be properly returned to the correct storage container at the end of the project. It is advantageous to have a sufficient work area, so that the whole collection can be laid out and viewed at the same time, and for the whole duration of the refitting process. If this is not possible, trays may be used to compare batches based on a certain criterion. In order to protect the artifacts from breakage, a protective foam sheet may be laid on top of the surface area.

Once taken out of their bags, the lithics, can be sorted into groups, based on attributes such as cortex variations, color, inclusions, technological stages, or into whole pieces and broken pieces. For example, broken pieces can be split into proximal ends (those with bottoms missing), mesial parts (those broken at both ends) and distal ends (those broken at the top). The size of the break may also be taken into consideration for the order in which they are sorted. Some minimum size limit of flakes may be established for large collections or for those where there are project time constraints. It is advisable to correlate the pieces with a contour map and site grid, in order to view the lithic densities and to understand the significance of where the pieces come from. For example, it may be beneficial to separate flakes into specific groups based on the densities in their distribution.

The lithics are refitted in a systematic way. Comparison of the pieces can be quite a laborious process, as some trial and error is involved at the beginning. However, with time it is possible to recognize various characteristics (such as color, size, texture or shape) from pieces that may have come from the same core. However, it is also important to note that in some cases, features can differ dramatically between pieces within the same block (e.g., if some of the flakes had been thermally altered through heating). Once the refitting for one batch has been completed, the next group may be done in the same manner, after which time the refitter may also compare the two groups for further possible refits. All conjoinable pieces should be recorded as found and glued together using a reversible adhesive (i.e., one that may be easily removed).

Conjoining is a very lengthy process, and it is difficult to find every potential refit. It is therefore necessary to decide how much refitting is sufficient for the goals of the analysis. Once all refitting has been accomplished, it is important to look at the lithic markings to see where they came from.Index cards can be used in order to record refit numbers and sketches may be made to document the position of lithics (i.e., whether joins are above or below other pieces). It can also be helpful to input the data onto a spreadsheet (each flake would be recorded as a separate entry and include such details as size, distance and reduction stage). Locations of the refits can then be plotted on a scaled graph in order to infer meaning from the patterns constructed.

SUMMARY

Although we don’t yet know the full potential of refitting, and many scholars are aware of the fact that it does have some limitations (for example, the recognition of discrete stages in the reduction process is not as straightforward as one would assume, and site formation processes are not entirely understood), refitting can nevertheless provide a fundamentally useful tool when viewed in the context of other pertinent information (such as microwear analysis). With careful and methodological application, refitting studies can provide us with crucial information relating to many aspects of archaeology.

Cortical surface or Cortex: A tough, dull-white powdery and porous coating found on the outer surface of newly exposed flint nodules. This may also include smooth weathered surfaces.

Debris or débitage: Waste material created during stone tool production.

Flake:A piece of stone material removed from a core or another flake by striking.

Knapper:Someone who works stone to create a tool by applying force to its surface, either by percussion or by pressure.

Lithics:Artifacts made of stone.

Microwear or usewear analysis: the study of the working edge of an artifact for signs of use. Patterns of wear, damage or residues may be observed via a high-powered microscope.

Palaeolithic or Paleolithic: Meaning the ‘Old Stone Age’ (between approximately 2.5 million and 20,000 years ago). It pertains to the prehistoric period from the time crude tool manufacturing activities began until the appearance of fully modern human hunting and gathering societies. This era demonstrates an evolution in human brain-size, together with a refinement in stone tool technology.

REDUCTION PROCESS/SEQUENCE or “chaîne opératoire”: The cumulative and irreversible removal of fragments from a core during the creation of a stone tool.